12 August 1992 Intelligent processing of focal plane arrays: sensors and controls for (Hg,Cd)Te LPE
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Abstract
Liquid phase epitaxy (LPE) is the preferred technique for growth of high quality (Hg,Cd)Te films for focal plane array applications. Successful implementation of this process in a manufacturing environment requires development of advanced sensors and process controls to increase yields and reduce costs. This paper will review progress on Ti's Intelligent Processing of Focal Plane Arrays program*. (Hg,Cd)Te LPE films are grown on (111)B-oriented (Cd,Zn)Te substrates in vertical dipping reactors in large (4500 g) molten solutions of mercury and cadmium in tellurium. Multiple (up to 8) substrates, for a total area of 54 cm2, can be run in a single growth cycle. The sensors and controls under development for this process include: (1) eddy current analysis (ECA) for detection of the liquidus temperature of the LPE growth solution, (2) electron beam microprobe/wavelength dispersive x-ray analysis (WDX) for rapid measurement of the film composition immediately after growth, (3) UV/visible optical absorption spectroscopy for determination of the mercury partial pressure over the growth solution, and (4) an RTD based precision temperature control system capable of improving capability from +/0.1 to +I- 0.02 C. ECA was found to be sensitive to the onset of crystallization on cooling in sample LPE melts. The WDX technique was found to be a rapid and accurate method for in-process film composition measurements. The impact of these IPFPA sensors and controls on total yield and producibility is discussed.
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Carlos A. Castro, Glenn H. Westphal, Luigi Colombo, "Intelligent processing of focal plane arrays: sensors and controls for (Hg,Cd)Te LPE", Proc. SPIE 1683, Infrared Focal Plane Array Producibility and Related Materials, (12 August 1992); doi: 10.1117/12.137779; https://doi.org/10.1117/12.137779
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